1. Technical Field
The present invention relates generally to an improved data processing system, and in particular, to a method and apparatus for processing graphics data. Still more particularly, the present invention provides a method and apparatus for displaying pixels without requiring window identifier support for overlay pixels.
2. Description of Related Art
Computer graphics concerns the synthesis or display of real or imaginary objects from computer-based models. In computer graphics systems, images are displayed on a display device to a user in two-dimensional and three-dimensional forms. These images are displayed using pixels. A pixel is short for a picture element. One spot in a rectilinear grid of thousands of such spots that are individually xe2x80x9cpaintedxe2x80x9d to form an image produced on the screen by a computer or on paper by a printer. A pixel is the smallest element that display or print hardware and software can manipulate in creating letters, numbers, or graphics. These pixels and information relating to these pixels are stored in a buffer. The information describing a pixel is identified using a window ID (WID). A WID is used as an index into a window attribute table (WAT). The WAT contains information describing how a pixel will be displayed on the screen. For example, a WAT identifies depth, colormap, buffer, and gamma for a pixel.
Typically, the WID is drawn into a separate buffer, which is used to describe how the pixels in the frame buffer or buffers will be displayed. Some graphics systems, such as, for example, UNIX servers, use overlays to enhance the performance of three-dimensional applications, which need to be overlaid on top of a three-dimensional application. An example of such is a menu. These types of servers typically require a separate WID buffer for the color planes and overlays so that multiple pixel interpretations can be supported on a per-pixel basis, which is required for transparent overlay support. A pixel interpretation is the way in which a pixel is displayed. Pixel interpretation involves displaying a pixel based on information or attributes associated or designated for the pixel, such as whether the pixel is 8 bits or 24 bits in depth. This pixel interpretation also includes other attributes, such as, for example, the colormap and the gamma map. Production of graphic cards that provide this support is expensive.
Therefore, it would be advantageous to have an improved method, apparatus, and computer instructions for providing overlay support without requiring dedicated WID hardware.
The present invention provides a method, apparatus, and computer instructions for displaying data. Each entry in a plurality of entries for an overlay window attribute table (WAT) is set with identical information in which a window identifier is unnecessary for accessing the information in the overlay WAT. Information in a color WAT is retrieved using the set of window identifiers in response to receiving a set of window identifiers. The information in the overlay WAT is retrieved without requiring the window identifier. Pixels are displayed on a display screen using the information retrieved from the color WAT and the information retrieved from the overlay WAT.